Adsorptive hydrogen storage in carbon and porous materials

The hydrogen adsorption and desorption isotherms of a highly pure single-walled carbon nanotube sample (SWCNT), a corresponding nitric acid-treated sample (A-SWCNT), two zeolites, and several kinds of activated carbon fibers (ACFs) were measured at 77 and 303 K over the hydrogen pressure range 0–3.5 MPa by using the high-pressure adsorption apparatus with sufficient accuracy. The amount of adsorbed hydrogen by weight depended on the micropore volume of the sample, except for the SWCNT and the A-SWCNT sample. The hydrogen storage capacity of A-SWCNT at a given micropore volume was higher than that of the zeolite and ACF samples. The specific surface area of micropore of A-SWCNT was 710 m2/g, whereas the theoretical surface area is 2630 m2/g. This finding suggests that the hydrogen storage capacity can be enhanced when the SWCNT has an ideal structure with a higher surface area.